The temperature-dependent action of sugar in the retardation and strength improvement of Ca(OH)2-Na2CO3-activated fly ash systems through calcium complexation

Abstract

This study reports the temperature-dependent strength improvement and retardation in Ca(OH)2-Na2CO3-activated fly ash binders with sugar. Without sugar, the system exhibited rapid stiffening due to the calcite formation. The addition of sugar clearly removed the false set; however, at room temperature, it retarded strength development because the calcium complexation of sugar inhibits the dissolved calcium ions from participating in calcite and C-S-H formation. However, at 90 °C, the use of sugar significantly improved the compressive strength by increasing the (1) degree of dissolution of fly ash and Ca(OH)2, (2) C-S-H formation, and (3) reduction of overall pore size and volume.